1. Field the Invention
Disclosed herein is a fused aerogel-polymer composite, methods of manufacture thereof and articles comprising the same.
2. Description of the Related Art
Aerogels are nanoporous materials having a porosity of at least 90% with a surface area of up to about 1000 m2/g. They are therefore low-density materials and can be either optically transparent or semi-transparent. Because of their low density, they are used for catalyst supports, in thermal and acoustic insulation, as well as in particle accelerators.
Silica aerogels are an example of aerogels that are used in a wide variety of applications. Aerogels are widely used as thermal insulation in refrigerators, freezers, and thermal reservoirs because of their high light transmittance and extremely low thermal conductivity. However, these materials are very brittle and undergo cracking and breaking upon being subjected to very small amounts of compression or impact. They are also easily damaged by the ingress of moisture into the pores.
In addition, because of the small pore size, silica aerogels are difficult to manufacture inexpensively. The small pore sizes lead to very large capillary forces that cause the silica aerogel to be easily crushed during drying. In order to overcome these capillary forces, the wet silica gel is subjected to supercritical extraction to produce the aerogels. Supercritical extraction uses high temperatures and high pressures. The use of supercritical extraction causes a dramatic increase in the cost as well as in the process time used for the manufacturing of the aerogels.
The brittleness and the low density of aerogels causes other problems in the processing of aerogels when it is desired to make a large piece of insulating composite that comprises the aerogel. Because of the low density of the aerogel, it is difficult to encapsulate the aerogel with a polymer to make a large monolithic composite without significantly altering the thermal insulating properties of the monolithic composite. In other words, because of the large volume occupied by the aerogel, a large amount of polymer has to be used to encapsulate the aerogel. This leads to a significant reduction in the capacity of the aerogel to act as a thermal insulator.
If a liquid polymer is used to bind the aerogel, the liquid enters the pores of the aerogel causing the aerogel to get crushed by the high capillary forces generated in the pores. This also leads to a reduction in the thermal insulating properties of the aerogel.
It is therefore desirable to manufacture an aerogel composite that retains the insulating properties of the aerogel while preventing or reducing the ingress of moisture or solvents into the pores of the aerogel.